Fabricating tunable metal sulfides embedded with honeycomb-structured N-doped carbon matrices for high-performance lithium-ion capacitors

Lithium-ion capacitors (LICs) are supposed to be a bridge of lithium-ion batteries (LIBs) and supercapacitors (SCs) and have been attracting intensive attention. Nevertheless, the battery-type anodes are cast in the shade owing to unsatisfactory kinetics, rate capability and lifespan induced by large volume swelling and low conductivity. Herein, we prepared core/shell crystalline/amorphous sulfides heterogenous nanoparticles encapsuled within 3D honeycomb-structured N-doped carbon matrices (Co-Sb-S@NC), the optimal Co-Sb-S@NC composite delivered excellent long-term durability (884.9 mAh/g at 1.0 A/g over 400 cycles) and superior rate performance (504.8 mAh/g at 3.0 A/g) with a significant pseudocapacitive-dominated behaviour. The superior performance could be attributed to the unique core–shell heterostructures and honeycomb-structured carbon matrices, in which the former induces enriched internal built-in electric field at the interfaces with directional ion mobility and the latter endows rapid charge transfer pathways and spatially-confined effect of refined particles during repeated electrochemical process. By optimizing the temperatures, types of cobalt salts and components ratios of heterostructures, furthermore, paired with commercial activated carbon (AC) to assemble LICs, a maximum power density of 5.91 kW kg−1 at an energy density of 65.7 Wh kg−1 and a minor capacity degradation of 0.002% per cycle during 10,000 loops at 5.0 A/g were exhibited. More encouragingly, the facile synthetic method could be extended to the fabrication of high-performance Fe-Sb-S@NC and Zn-Sb-S@NC electrodes towards potential application for advanced LICs.